The invention relates to an apparatus for gas recirculation in an internal combustion engine, particularly exhaust gas or the gas of a crankcase ventilator.
It is known, for instance, from U.S. Pat. Nos. 4,258,687 and 4,267,812 (=DE 30 34 971) that exhaust gases of an internal combustion engine can be recirculated from the exhaust pipe to the intake duct of the internal combustion engine. In these known arrangements, the recirculated exhaust gases are fed into the intake pipe without filtering. This is not a problem at relatively low recirculation rates. However, at high recirculation rates of 40-50%, which are necessary, for instance, in internal combustion engines with direct injection, there is such a pronounced amount of soot that a substantial accumulation of dirt in the intake pipe has to be expected.
Particularly a combined application of exhaust gas recirculation and gas supply from a crankcase ventilator (so-called blow-by) has the disadvantage of producing a sticky and tightly adhering mass of dirt. These deposits along the walls of the intake pipe reduce the flow cross sections. Furthermore, if the gases are introduced into switchable intake pipes in front of the switching elements, deposits on the switching elements will adversely affect their switching and/or sealing function. Deposits on the intake valves can also impair function.
It is the object of the invention to provide an apparatus for recirculating exhaust gases in which significant dirt accumulations are avoided.
This and other objects of the invention are achieved by providing an apparatus for gas recirculation in an internal combustion engine comprising a connecting line leading from a recirculation gas source to a connection to the intake device of the engine, wherein a filter element is arranged in the connecting line between the recirculation gas source and the connection to the intake device of the internal combustion engine. The recirculation gas source may be, for example, an internal combustion engine exhaust line or an internal combustion engine crankcase ventilator.
In a first embodiment of the invention, the gas recirculation apparatus is advantageously designed in such a way that a filter element is arranged in the connecting line between the exhaust pipe and the connection on the intake device of the internal combustion engine.
According to a second embodiment, a filter element is likewise advantageously arranged in the connecting line between the connection of a crankcase ventilator and the connection on the intake device of the internal combustion engine.
Connecting the filter according to the invention in the incoming line makes it readily possible to remove the soot from the recirculated gas so that, for instance, only the hot exhaust gas is supplied to the internal combustion engine or to the intake duct. The filter is preferably provided with a highly heat-resistant filter medium, such as a pressed part made of a high-grade steel. Due to a possibly high dirt accumulation, the filter element could be replaced at the same interval as the air filter, which has to be monitored in any case.
According to one advantageous embodiment, the filter element can be configured as an inline filter or, for assembly reasons, it can also be integrated into the exhaust gas recirculation flange of the intake pipe.
In accordance with another advantageous embodiment of the invention, a cyclone separator can be connected upstream of the filter element. This cyclone separator removes coarse soot particles and thus helps increase the service life of the filter element. It is of course also possible to use a cyclone separator as the filter element without providing an additional filter. In this case it is advantageous to use a multi-cell cyclone separator with high collection efficiency.
In yet another advantageous embodiment of the invention, cleaning is effected by electrical energy. At regular intervals, the filter medium is heated to above the burning temperature of the soot by applying an electrical voltage, and the soot is burned. The combustion gases can be fed into the exhaust gas duct of the internal combustion engine via a corresponding line.
An additional alternative to the interposition of a filter element is the use of an electrostatic separator. Such a separator is highly efficient and has a low xcex94p. The electrostatic separator can also be cleaned by heating.
A further embodiment of the invention involves the use of an easily replaceable filter as the filter element. To simplify the replacement of the filter element within a certain maintenance cycle, the filter element is arranged in an easy-change filter that can be unscrewed. This easy-change filter resembles an easy-change oil filter and can be readily disposed of, for instance by incineration.
These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or in the drawings, and the individual features each may be implemented in embodiments of the invention either individually or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.